Jamieson, Fausset & Brown

The "ye" is emphatical, from its position in the Greek, "Ye brethren"; as opposed to those legalists "who trouble you." unto liberty--The Greek expresses, "on a footing of liberty." The state or condition in which ye have been called to salvation, is one of liberty. Gospel liberty consists in three things, freedom from the Mosaic yoke, from sin, and from slavish fear. only, &c.--Translate, "Only turn not your liberty into an occasion for the flesh." Do not give the flesh the handle or pretext (Rom 7:8, "occasion") for its indulgence which it eagerly seeks for; do not let it make Christian "liberty" its pretext for indulgence (Gal 5:16-17; Pe1 2:16; Pe2 2:19; Jde 1:4). but by love serve one another--Greek, "Be servants (be in bondage) to one another." If ye must be servants, then be servants to one another in love. While free as to legalism, be bound by Love (the article in the Greek personifies love in the abstract) to serve one another (Co1 9:19). Here he hints at their unloving strifes springing out of lust of power. "For the lust of power is the mother of heresies" [CHRYSOSTOM].